Characterization of "significant adverse ecotoxicological effects" of persistent organic pollutants (POPs) presents particular challenges. In the various international conventions on POPs and persistent, bioaccumulative, and toxic substances, guidance on classification is not detailed and, in some cases, is unclear. This paper focuses on several key issues in relation to selection of assessment endpoints, use of appropriate effect measures, and uncertainty in the face of limited data. Because POPs are persistent and bioaccumulative, measures of effect should be based not on concentrations in environmental matrices but rather on residues in the body of the organism or in tissues that are causally linked to adverse responses. To obtain these data, currently used toxicity testing methods may need to be modified or substantiated by toxicokinetic information to ensure that substances with POP-like properties are adequately characterized. These data can be more easily matched to environmental monitoring measurements of body or tissue residues for the purposes of assessing whether adverse effects occur in the environment. In the face of persistence and accumulation in the food chain, and considering the extent and suitability of available data, a suitable policy on the use of uncertainty factors may need to be applied when making judgments about toxicity. This paper offers guidance that can be used to identify candidate POPs that have the potential to cause significant adverse effects in the ecosystem.

There is a growing sense of urgency among scientists and environmental policy-makers concerning the need for improving the scientific foundation supporting international regulations for identifying and evaluating persistent, bioaccumulative, and toxic (PBT) substances and persistent organic pollutants (POPs) in the environment. The current national and international regulations define PBTs and POPs in terms of fairly strict criteria that are based on the state of the science in the late 1970s and early 1980s. Since then, an evolution in the state of the science has produced new insights into PBT substances and an array of new methods to identify PBT chemicals. The development of regulatory criteria has not kept up with the rapid development in environmental chemistry and toxicology, and as a result, scientists often find themselves in the situation where guidance on PBT and POPs criteria is limited and, in some respects, out of date. With this background, a Society of Environmental Toxicology and Chemistry (SETAC) Pellston Workshop brought together experts from academia, government, and industry to reach consensus on the significance of advancements in our understanding of the behavior and potential impact of POPs and PBTs in the environment, the current understanding of the state of the science, as well as recommendations for policy-makers to improve and coordinate national and international regulations on this issue. The workshop builds on the outcome of a previous Pellston workshop, held in 1998, which focused on the evaluation of persistence and long-range transport of organic chemicals in the environment, and is linked to other recent Pellston workshops, among them the Tissue Residue Approach for Toxicity Assessment workshop held in 2007. The results of this workshop are conveyed in a series of 9 articles, published in this issue of Integrated Environmental Assessment and Management, and describe the coordination of science, regulation, and management needed to more effectively achieve a common goal of managing chemicals on our planet.

The draft European Commission's Directorate General for Health and Consumer Policy (DG SANCO) document represents the state of the art in environmental risk assessment (ERA) including new trends and combining high level environmental protection and realism. Using the ecosystem services concept, it offers a promising approach to determine which impact may be tolerable, where, and when. Established ERA uses a stepwise approach starting with standardized internationally accepted studies combined with appropriate assessment factors (AFs) and where needed followed by higher tier assessments and respective adjusted AFs. The draft SANCO document follows this approach and presents additional refinements to improve the realism of risk assessment, which is desirable; however, that such additional data becomes a standard requirement without a clear need must be avoided. The idea of additional AFs presented in parts of this article should accordingly first consider risks and benefits in line with this approach and only be requested if data indicates their necessity. In addition, the suggested focus on uncertainty analysis without any obvious according benefits in terms of reduced assessment factors where uncertainty is reduced, is still a challenge. The requirement for science- and/or data-based relevant concerns before requesting more data, and the list of requirements for new innovative approaches that should be met before such approaches can be used in regulatory ecological risk assessments, is well-founded and strongly supported. Modeling has been included in ERA to allow extrapolation of risk assessments without the need of excessive (animal) testing; it will also address uncertainties more quantitatively. However, this should be done in an overall realistic ecological assessment; simply adding up various individual uncertainties and worst-case assumptions must be avoided, as this is counterproductive for the use of this valuable tool. The need for expert judgment should be low at the lower tiers of ERA; however, more complex and less standard ERA will still require significant expertise.